Hermetically sealed switching device with bellows



April 1966 P. RAVRET ETAL 3,244,849

HERMETICALLY SEALED SWITCHING DEVICE WITH BELLOWS Filed April 21, 1964 2Sheets-Sheet 1 lnre alone Pity-re Quay-4i Laulk' e- 40;

April 5, 1966 P. RAVRET ETAL 3,244,849

HERMETICALLY SEALED SWITCHING DEVICE WITH BELLOWS Filed April 21, 1964 2Sheets-Sheet 2 United States Patent 6 12 Claims. (or. 200-168) Thepresent invention, which is due to Mr. Louis Miachon and to Mr. PierreRavret, relates to an electric switch enclosed in an envelope whichhermetically seals it from theam bient medium, the temperature and/orpressure of which are likely to vary between very wide limits, and thisswitch is materially actuated from the outsideby way of an elasticdeformation of the said envelope. By switch is meant any device intendedto establish and/or break one ormore electric circuits, that is tosay,it also includes a reversing switch, a circuit breaker, a change-overswitch, etc.

One disadvantage of previously known constructions ofthis type ist'hatthe envelope may undergo, in its elastic part, deformations which modifythe characteristics of the apparatus when the said temperature andpressure variations are large.

This disadvantage is obviated in the apparatus accordingwto theinvention, which for this purpose is characterised in that the electricswitch is enclosed in a substan-. tially. cylindrical bellows comprisingan upper end member, and of which the opposite end is closed by aninsulating base supporting the said electric switch, the upper endmember and the said opposite end of the bellows beingheld fast inrelation to one another, the lateral wall being. resilient andpleated,,the folds being symmetrical in relation tothe axis of thebellows, and the switch beingoperated with the aid of two actuatingmembers so disposed as to control one another through one of the foldsof the bellows,.one of the said actuating members being outside and theother inside the said bellows.

By way of non-limiting example, there is hereinafter described ahermetic switching device according to the invention in which the switchproper is a miniature quickbreakreversing switch.

FIGURE 1 illustrates a section through the apparatus along a verticalplane extending along the axis of the bellows.

FIGURE 2 illustrates .a portion of the actuating memher outside thebellows.

FIGURE 3 illustrates a variant of the connection between the bellows andthe base.

In these figures, 1 denotes a cylindrical insulating'base, for exampleof ceramic material, to the metallized pe riphery of which there issoldered at 2 theedge of a rigid cylindrical casing 3. The said casingmay consist of stainless steel. A lbellows 4 of substantiallycylindrical form is welded or solderedlat Sto thefinner surface ofthe'peripheral wall of the casing 3; The material of which the saidbellows consists may be, for example, an iron-chromium compound or anyother product having high characteristics of elasticity and resistanceto oxidation in considerable temperature and pressure ranges, forexample -100 C. to +600 C., and from to 3.10 Pascal.

The end member 4a of the bellows is welded or soldered to a ring ortransverse member 7, for example in its central region 6. The said ringis made fast with the end 3a of the casing .3 by three screws orconnecting means 8 disposed at 120 apart around the axis XY of thedevice. This arrangement maintains the end memice her of the bellows andthe opposite extremity of the latter at a constant distance apart.

Approximately the upper half of the bellows 4 can 'be inscribedwithin acylindrical surface whose diameter is smaller than that of a cylindricalsurface corresponding to the lower half of the bellows, so that thereexists an annular space between the said upper half of the bellows andthe inner surface of the peripheral wall Olf the casing i3. Disposed inthis space is the skirt 9a of a hollow cylindrical push member 9,of.which the upper endcomprises an external extension 9b forming acontrol button, which extends through the end 3a of the casing 3. Thesaid push member 9 is formed with holes for the free passage of thescrews 8 and of the corresponding portions of the ring 7. It bearsagainst a crescent-shaped-rnernlber 10 (shownin plan view in FIGURE 2)which is inserted in the centre fold 4b of the bellows 4.

The assembly comprising the push member 9 and the member 16 forms theouter actuating member of a switch. The inner actuating member of theswitch is formed of a push member 11 extended by a rod 12 which directlyactuates. the movable portion of the switch proper. The said push membermay be made fast with the bellowsof at least a part of the inner surfaceof the centre fold.

The utilisation of this centre fold for effecting the connection of thet-wo actuating members substantially equa-lizes the stresses on themetal of the bellows in the different folds. The connection could alsobe effected by means of a fold other than the centre fold.

The switch proper is a reversing switch of known construction includinga resilient blade. One end 14aof the said blade 14 is fixed into the endof an output terminal 13, while the other end 14b carries a contact stud15 cooperating with counter contacts 16 and 17 respectively' disposed atthe end of other output terminals 18, 19. These terminals are passedthrough the base 1 in fluid-tight manner by the following means:

The terminals 13, 18, 19, are hollow metal pins which have substantiallythe same expansion coefiicient as the base 1 to which they are welded orsoldered in hermetic fashion at 20, 21 and 22 respectively; They areeach traversed by a conductor respectively designated with the numerals23, 24, 25, having good electrical conductivity, for example of copper,of which the outer end serves as a connecting means.

The inner end of the conductor 23 is electrically connected in anyappropriate manner to the end 14a of the blade 14. The inner ends of theconductors 14 and 25 may form the-fixed contacts 16, 17, either bythemselves or in association with contactmembers made ofa materialpossessing particular electrical and mechanical characteristics, suchasgold, for example. These conductors 24 and 25 are hermetically weldedat Z6; Z7, to'the pins 18, 19.

The inner end of the pin 13 is formed with an aperture 28 which providescommunication between the interior of the device and the exterior by wayof the clearance between the conductor 23 and the longitu dinal apertureof the pin. When the fitting of the various parts of the device has beencompleted, including the welding of the pins 18" and 19, the aforesaidclearance and the said aperture 28 are utilised to fill the interior ofthe bellows 4 with a gas having appropriate physical and chemicalcharacteristics; The conductor 23 is thereafter hermetically welded tothe pin 13 at 29.

In its central region, the blade 14 is traversed by the rod 12. Thedisplacement of the latter along the axis XY causes a change in thecamber of the blade 14 and consequently the sudden movement of thecontact stud 15 from the contact 16 to the contact 17 or vice versa.

Patented Apr... 5, 19.66

The displacement of the rod 12 results either from a force being appliedto the button 912 or from the force of a return spring 30 disposedbetween the push rod 12 and the base 1. It is limited in one directionby the base 1 and in the other direction by the end 3a of the jacket 3,whereby unnecessary deformations of the bellows 4 are avoided.

Owing to the fact that the ends of the said bellows are maintained at afixed distance and the folds are symmetrical in relation to the axis XY,the theoretical component along the axis XY of the geometrical sum ofthe forces emanating from the external and internal pressures is zero.Under these conditions, the folds do not undergo any appreciabledeformation when the ternperature and/ or the pressure of the ambientmedia vary. Consequently, the force to be exerted on the button 9b orthe force of the return spring 30, which are both directed along XY, areindependent of the said variations.

Many constructional variations are possible. For example, as is shown inFIGURE 3, the end of the bellows 4 may be reinforced and directlysoldered at 31 to the base 1, the end of the casing 3 then being weldedat 32 to the said end of the bellows. The end 4a of the bellows may bemaintained in contact with the fixed member 7 by an appropriate pressureexerted within the bellows.

Likewise, and in accordance with the conditions of use of the device,the switch may be of a different type, the metallic parts forming theelectric contacts proper may have any appropriate form, etc.

What we claim is:

1. A hermetically sealed switching device comprising, in combination,substantially cylindrical bellows having a closed end, an opposite openend, and a plurality of corrugations between said ends; closure meansextending transversely to said open end of said bellows fluid tightlyconnected thereto for closing the same; rigid connecting meansinterconnecting said closure means and said closed end of said bellowsfor maintaing said opposite end of said bellows spaced a fixed distancefrom said closed end thereof; switch means supported in the interior ofsaid bellows on said closure means; and a pair of actuating means foractuating said switch means, one of said actuating means being locatedoutside of said bellows and having a free actuating end and engaging atthe other end thereof to the outer surface of one corrugation of saidbellows, and the other actuating means being located in the interior ofsaid bellows and engaging at one end thereof to the inner surface ofsaid one corrugation and being connected at the other end thereof tosaid switch means.

2. A hermetically sealed switching device as set forth in claim 1,wherein said actuating means are arranged coaxially with said bellows.

3. A hermetically sealed switching device as set forth in claim 1,wherein said rigid connecting means comprise casing means completelycovering said bellows, said opposite ends of said bellows being fixed tosaid casing means.

4. A hermetically sealed switching device as set forth in claim 1,wherein said casing means are constructed to form a guide for said oneactuating means.

5. A hermetically sealed switching device as set forth in claim 3,wherein said bellows and said casing means are formed from metal.

6. A hermetically sealed switching device as set forth in claim 5,wherein said casing means comprise a cupshaped member having atransverse end wall at one end,

said closure means being in the form of a substantially plate-shapedmember extending transversely through the other end of said cup-shapedmember and being fluid tightly connected thereto, and said one actuatingmeans having an operating portion projecting through a central openingin said transverse end wall to the outside of the casing means.

7. A hermetically sealed switching device as set forth in claim 6,wherein said casing means comprise further a transverse member extendingspaced from and substantially parallel to said transverse end wall ofsaid cupshaped member forming part of said casing means, and connectingmeans connecting said transverse member to said transverse end wall,said one actuating means comprise a second cup-shaped member having atone end thereof a transverse wall located between said transverse endwall and said transverse member of said casing means and being formedwith openings through which said connecting means extend, said operatingportion of said one actuating means projecting from said transverse wallof said second cup-shaped member through said central opening in saidtransverse end Wall and said closed end of said bellows abutting againstsaid tansverse member.

8. A hermetically sealed switching device as set forth in claim 7,wherein said closed end of said bellows is fixedly held on saidtransverse member of said casing means by internal pressure in saidbellows.

9. A hermetically sealed switching device as set forth in claim 7,wherein said closed end of said bellows is bonded at a central portionthereof to said transverse member of said casing means.

10. A hermetically sealed switching device as set forth in claim 7,wherein said one actuating means comprises further as second transversemember fixed to the other end of said second cup-shaped memberand'engaging with an inner portion thereof said one corrugation.

11. A hermetically sealed switching device as set forth in claim 1,wherein said closure means comprises a substantially plate-shaped memberof insulating material and wherein said switch means comprise at leasttwo terminal members, each terminal member including a hollow pinextending through said plate-shaped member and having an expansioncoefficient substantially equal to that of said plate-shaped member andbeing fluid tightly joined to the latter, and an electric conductorextending through the interior of said hollow pin fluid tightly weldedthereto at least at the outer end of the latter.

12. A hermetically sealed switching device as set forth in claim 11,wherein one of said pins is formed with an aperture communicating withthe interior of said bellows and wherein the conductor in said onehollow pin has at least between said aperture and said outer end of saidpin a diameter smaller than the inner diameter of said hollow pin so asto form an annular passage between said conductor and said one pin sothat the interior of said bellows may be filled with a gas of desiredcomposi tion and pressure through said annular passage before saidconductor is fluid tightly welded to the outer end of said one pin.

References Cited by the Examiner UNITED STATES PATENTS 1,706,523 3/1929Churcher 200-168 3,038,980 6/1962 Lee 200-144 3,174,019 3/1965 Jansson200-144 KATHLEEN H. CLAFFY, Primary Examiner,

H. O. JONES, Assistant Examiner,

1. A HERMETICALLY SEALED SWITCHING DEVICE COMPRISING, IN COMBINATION,SUBSTANTIALLY CYLINDRICAL BELLOWS HAVING A CLOSED END, AN OPPOSITE OPENEND, AND A PLURALITY OF CORRUGATIONS BETWEEN SAID ENDS; CLOSURE MEANSEXTENDING TRANSVERSELY TO SAID OPEN END OF SAID BELLOWS FLUID TIGHTLYCONNECTED THERETO FOR CLOSING THE SAME; RIGID CONNECTING MEANSINTERCONNECTING SAID CLOSURE MEANS AND SAID CLOSED END OF SAID BELLOWSFOR MAINTAING SAID OPPOSITE END OF SAID BELLOWS SPACED A FIXED DISTANCEFROM SAID CLOSED END THEREOF; SWITCH MEANS SUPPORTED IN THE INTERIOR OFSAID BELLOWS ON SAID CLOSURE MEANS; AND A PAIR OF ACTUATING MEANS FORACTUATING SAID SWITCH MEANS, ONE OF SAID ACTUATING MEANS BEING LOCATEDOUTSIDE OF SAID BELLOWS AND HAVING A FREE ACTUATING END AND ENGAGING ATTHE OTHER END THEREOF TO THE OUTER SURFACE OF ONE CORRUGATION OF SAIDBELLOWS, AND THE OTHER ACTUATING MEANS BEING LOCATED IN THE INTERIOR OFSAID BELLOWS AND ENGAGING AT ONE END THEREOF TO THE INNER SURFACE OFSAID ONE CORRUGATION AND BEING CONNECTED AT THE OTHER END THEREOF TOSAID SWITCH MEANS.